2,2-Dibromo-3-nitrilopropionamide (DBNPA) is a biocide which is used in industrial water treatment, cooling systems and paper mills. DBNPA is an efficient biocide with a rapid microbiocidal broad-spectrum activity, especially in water systems that contain high organic loads.
The main current application of DBNPA is as a liquid formulation, which contains a mixture of water and an organic solvent such as a glycol (for example, polyethylene glycol (PEG), dipropylene glycol (DPG), ethylene glycol, etc.) and others. The active ingredient (DBNPA) is only 5-25% of such liquid formulation. The addition of an organic solvent is required for dissolution of the relatively water-insoluble DBNPA into a liquid formulation.
Prior art teaches the production of DBNPA as a powdered material which can be used for the preparation of a liquid or solid formulation.
Several types of sustained-release compositions containing DBNPA have been described:    1) EP 285 209 recites a solid sustained release antimicrobial composition (in a tablet form), comprising 1 to 90% by wt of a halogenated amide (including DBNPA) antimicrobial agent, 10 to 80% by wt of a hydrophilic polymer, 0 to 80% by wt of a compression agent and 0 to 10% by wt of a mold release agent. A composition comprising 40% DBNPA, 30% Methocel (water soluble cellulose polymer), 27% CaHPO4 (as compressing agent) and 3% stearic acid, was specifically demonstrated.    2) WO 98/25458 discloses a solid sustained-release tablet consisting of DBNPA admixed with a water-soluble natural or synthetic polymer. Besides the addition of a synthetic polymer into the formulation, the tablet is coated with an additional water-soluble cellulosic polymer.    3) WO 99/18162 discloses a biocidal powder coating composition comprising thermoplastic and/or thermosetting resins based on epoxy, polyester, acrylic or polyurethane resins. The biocide used is a liquid bio-active material (including DBNPA) and/or specially selected solid bio-active materials (for example, solid thiazine-thiones, thiolphthalimides, and others). The biocides are homogeneously mixed or bonded with the particles of the powder.
The process of preparing said biocidal powder coating composition is characterized by blending the components of the powder coating composition in a premixer, followed by feeding the mixture into an extruder, heating to a temperature high enough to melt and mix most of the major components, and cooling to a solid form.    4) EP 953 284 discloses a composition (in a tablet form) for delivering the DBNPA biocide to an oil field fracturing fluid, comprising effervescing agents such as sodium bicarbonate, citric acid and borax. The composition comprises about 35-65% DBNPA, about 15-28% sodium carbonate, 15-27% citric acid and up to about 20% borax.    5) EP 954 966 recites controlled release compositions comprising a biologically active compound, including DBNPA, and a hydroxystyrene polymer (e.g. hydroxystyrene homopolymer, methylhydroxystyrene homopolymer, halohydroxystyrene homopolymer and their copolymers). The weight ratio of DBNPA to the polymer is from 0.1:99.9 to 95:5.
The above prior art is related to sustained-release formulations (including in a tablet form) which contain various additives, such as polymeric matrix, binders and compression agents in significant amount. However, no free DBNPA compound in a compacted form has been used and/or described in the literature. The ability to provide an almost net content of the active compacted material (such as in a tablet, granule, pellet or briquette form) is most certainly a significant advantage.
The handling of the existing DBNPA powdered solid material requires severe safety precautions due to the hazardous nature of this biocide, especially in a fine powdered form.
An additional problem concerning the application of powdered DBNPA, is the tendency of the powder to agglomerate, creating lumps and a bulky material. This phenomenon reduces the flowability of the product and causes handling and safety problems.
In view of these disadvantages of powdered DBNPA there is a need for a safer, easy to handle and user-friendly densified particulate DBNPA. Such DBNPA should be free of said agglomeration phenomena. As was mentioned above, the densified forms known in the art have the considerable drawback of requiring the addition of binders and fillers to obtain suitable solid forms of the biocide. Therefore, compacted forms known in the art do not provide net or almost net contents of active material in the tablet, granule, briquette or pellet form. It has now been found that it is possible to prepare compacted forms of DBNPA which have sufficient strength and provide a slow release of the active material into the water without losing their compacted nature. It has further been surprisingly found that it is possible to prepare compacted forms of this biocide, without employing any binder or filler.
It is an object of the present invention to provide a compacted DBNPA particle in a granular and/or a tablet and/or a briquette and/or a pellet form. It is a further object of the present invention to provide a compacted DBNPA particle having a diameter larger than 0.5 mm., with no binder, filler or additive added. Yet a further object of the present invention is to provide a compacted DBNPA particle that contains from 0 to about 3 wt % of water content. It is yet another object of the present invention to provide a non-agglomerative DBNPA.